Cranial bone flap fixation system and method

Abstract

A cranial bone and bone flap fixation device, comprising first and second caps between which portions of the cranial bone and bone flap are to be gripped; a mounting post located to allow relative cap movement lengthwise of an axis defined by the post, at least the first cap, which is movable lengthwise of the post, forming peripheral petals that are spaced apart about an axis and radially outwardly of a central body portion of the cap, whereby the petals are individually and resiliently movable relative to the central body portion in directions generally parallel to the axis, and in response to gripping.

1. The method of affixing a bone flap to an adjacent cranial zone, that includes
 a) providing first and second caps between which portions of the cranial bone and bone flap are to be gripped, 
 b) providing a mounting post located to allow relative cap movement lengthwise of an axis defined by the post, 
 c) providing at least the first cap with peripheral petals that are spaced apart about said axis and radially outwardly of a guide defined by a central body portion of the cap, whereby the petals are individually and resiliently movable relative to said central body portion in directions generally parallel to said axis, and in response to said gripping, 
 d) said guide having a thin frusto-conical side wall tapering toward and adapted to penetrate gaps of different widths between said bone flap and proximate cranial bone, said thin tapering side wall locally engaging edges of said bone flap and of said cranial bone, and there being a thin annular lower wall of the guide integral with said tapering side wall and projecting toward the post to form a central opening for passing the post, and there also being at least three tabs confined at and proximate said central opening, said tabs having narrowed flexure zones integral with said lower wall and heads spaced about the post and extending proximate the post and angled toward an interior void bounded by said tapering side wall, for interfering engagement with serrations on the post, as the cap is tightened axially along the post, said tabs everywhere confined below the upper half of said void, 
 e) relatively displacing the caps toward one another whereby cap petals are engaged with at least the bone flap or the adjacent cranial bone, and to conformingly retain the caps including said petals to opposite sides of the flap and the cranial bone, 
 f) tightening the caps relatively toward one another into positions wherein relative separation of the caps is blocked, petals are resiliently flexed, and post extent between the caps is tensioned, and wherein the second cap is pulled in an upward direction as the first cap is tightened downwardly. 
 
   
   
     2. The method of  claim 1  including the step of causing said guide to orient the cap transversely as the cap petals approach or engage bone flap and cranial bone surfaces. 
   
   
     3. The method of  claim 1  wherein said petals are formed as outward continuations of said guide frusto-conical wall. 
   
   
     4. The method of  claim 1  wherein said tabs are provided to have widths less than their lengths, and define tips that have ratcheting engagement with said serrations. 
   
   
     5. The method of  claim 1  wherein the number of said tabs is less than the number of said petals, on said one cap. 
   
   
     6. The method of affixing a bone flap to an adjacent cranial zone, that includes
 a) providing first and second caps between which portions of the cranial bone and bone flap are to be gripped, 
 b) providing a mounting post located to allow relative cap movement lengthwise of an axis defined by the post, 
 c) providing a guide on the first cap, said guide having a thin frusto-conical side wall tapering toward and adapted to penetrate gaps of different widths between said bone flap and proximate cranial bone, said thin tapering side wall locally engaging edges of said bone flap and of said cranial bone, and there being a thin annular lower wall of the guide integral with said tapering side wall and projecting toward the post to form a central opening for passing the post, and there also being at least three tabs confined at and proximate said central opening, said tabs having narrowed flexure zones integral with said lower wall and heads spaced about the post and extending proximate the post and angled toward an interior void bounded by said tapering side wall, for interfering engagement with serrations on the post, as the cap is tightened axially along the post, said tabs everywhere confined below the upper half of said void, 
 d) relatively displacing the caps toward one another to first engage one cap with the underside of at least the bone flap or the adjacent cranial bone, 
 e) and then tightening the caps relatively toward one another into positions wherein relative separation of the caps is blocked, and wherein the second cap pulled upwardly as the first cap is tightened relatively downwardly. 
 
   
   
     7. The method of  claim 6  including causing said guide to laterally orient the first cap to have approximately equal lateral extents thereof adjacent cranial bone and bone flap surfaces. 
   
   
     8. The method of  claim 6  wherein the second cap is pulled upwardly by pulling the post upwardly. 
   
   
     9. The method of  claim 8  wherein the post is pulled upwardly to effect engagement of the second cap with cranial bone. 
   
   
     10. The method of  claim 9  wherein the first cap is displaced downwardly relative to the post, and until it becomes tightened against the upper side of cranial bone. 
   
   
     11. The method of  claim 10  wherein a hand manipulable applicator is provided and used to effect said upward pulling of the post, and said downward displacement of the first cap. 
   
   
     12. The method of affixing a bone flap to a cranial bone, using the following:
 a) first and second caps between which portions of the cranial bone and bone flap are to be gripped, 
 b) a mounting post located to allow relative cap movement lengthwise of an axis defined by the post, 
 c) at least the first cap forming peripheral petals that are spaced apart about said axis and radially outwardly of a central cup shaped guide defined by the cap, whereby the petals are individually and resiliently movable relative to said central guide in directions generally parallel to said axis, and in response to said gripping, said first cap being movable lengthwise of the post, said method including the steps: 
 d) said guide having a thin frusto-conical side wall tapering toward and adapted to penetrate gaps of different widths between said bone flap and proximate cranial bone, said thin tapering side wall locally engaging edges of said bone flap and of said cranial bone, and there being a thin annular lower wall of the guide integral with said tapering side wall and projecting toward the post to form a central opening for passing the post, and there also being at least three tabs confined at and proximate said central opening, said tabs having narrowed flexure zones integral with said lower wall and heads spaced about the post and extending proximate the post and angled toward an interior void bounded by said tapering side wall, for interfering engagement with serrations on the post, as the cap is tightened axially along the post, said tabs everywhere confined below the upper half of said void, 
 e) relatively displacing the caps toward one another to first engage one cap with the underside of at least the bone flap or the adjacent cranial bone, 
 f) and then tightening the caps relatively toward one another into positions wherein relative separation of the caps is blocked, the second cap being pulled upwardly as the first cap is tightened downwardly. 
 
   
   
     13. The method of  claim 12  wherein the first cap is displaced downwardly relative to the post, and until it becomes tightened against the upper side of cranial bone. 
   
   
     14. The method of  claim 13  wherein a post displacing instrument is provided and used to effect said upward pulling of the post, and said downward displacement of the first cap. 
   
   
     15. The method of  claim 14  wherein the first cap is displaced downwardly relative to the post, and until it becomes tightened against the upper side of cranial bone. 
   
   
     16. The method of  claim 15  wherein said post displacing instrument has a gripper part used to effect said upward pulling of the post, and another part to effect said downward displacement of the first cap. 
   
   
     17. The method of  claim 15  wherein said instrument includes two hand manipulable parts, and including the step of squeezing said parts toward one another to effect said upward pulling of the post and said downward displacement of the first cap.